[Qgis-user] Re: Image boundary

[Agustin Lobo]

Luiz,

motta.luiz at gmail.com wrote:
> Agustin,
> 
> Thank´s for your interest.
> 
> I have some doubts:
> 1) Do you want two coordenates in table, Geographic and the reference 
> system of image ?
> Ex.: Long, Lat, X, Y

Yes, for each corner

> 2) Are the coners of real image (calculate the first valid pixel) or  
> extend of image (read header of file) ?
> 
> The name is because the corners are calculated, the boundary of image 
> with valid pixels (no Zero).
> 
> The bounding box is the extend of all image (include the all pixes) , 
> rectangle where image is here.
>

You are right, I was wrong. The bounding box is the rectangle defined by the 
extent (minX,minY to maxX,maxY or minLon,minLat to maxLon,maxLat)
Those coordinates would be included in the 16 coordinates (2 pairs for each 
corner) of the 4 corners.

A plugin for generating polygons of the bounding box of each image would be a 
different one. It would be interesting also, but your current image boundary is 
more interesting as you see the actual location of the images. Perhaps you could
call it "Image footprints"? But this is not an important issue.

Thanks and sorry for the confusion!

Agus

> Regards,
> Luiz
> 
> 
> Agustin Lobo escreveu:
>> Luiz,
>>
>> I would suggest including the coordinates of the 4 corners of each 
>> image in the
>> table of the shape file, best in lon, lat and in projected
>> coordinates. This would make
>> a lot of fields (16) as images are seldom in lon,lat, but that would
>> not hurt and
>> would be very useful. Also, a more conventional name for this plugin
>> would be bounding box.
>>
>> Obrigado!
>>
>> Agus
>>   
> 
>